Automatic Solder Paste Printer Positional Feedback Control

Abstract

Stencil printing is a critical first step in surface mount assembly. It is often cited that the solder paste printing operation causes about 50%-80% of the defects found in the assembly of PCBs. Printing is widely recognized as a complex process whose optimal performance depends on the adjustment of a substantial number of parameters. It is not uncommon to hear that stencil printing is more of an “art” than “science”. In fact, the process is so complex that sub-optimal print parameters usually end up being used. In addition, stencil printing produce relatively noisy data, which makes the print process extremely difficult to control. Ideally, minimizing the variance of the deposited location and volumes will improve the quality of the process and produce more reliable solder joints.

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Stainless steel foil stencils are used to print solder paste and adhesives on bare PCBs. Stencils of varying thickness, and also ‘step’ stencils with varying thicknesses in specific areas for different deposition requirements are used.
Solder Paste, a complex mixture of tiny particles of solder alloy and flux vehicle, is a challenging material to print onto a bare Surface Mount Technology (SMT) PCB.
Traditional metal screens excel in the printing of many electronic materials on rigid and flexible PCBs. These materials include solder masks and resists, fluxes and solder pastes, and especially conductive inks (silver, carbon, silver chloride), and dielectric inks, both used to form conductive traces, capacitor and resistor elements.
MPM stencil printers pioneered Surface Mount Technology (SMT) solder paste printing and continue to lead the industry in performance and excellence in printing electronic materials, including SMT Solder Paste.
PrintingMPM printers are high-speed, high-precision systems for depositing precise patterns of solder paste on printed circuit boards through foil stencils. Available in a wide range of capabilities.Best-in-class printing performance has always neen a hallmark of MPM printing technology, the recognized world standard for reliability, throughput, and high yields.